In order to produce a dental prosthesis such as a crown or a bridge, a surgeon or dentist must first prepare the tooth or teeth that will serve as support for the prosthesis. This is done by milling and forming the tooth into a stump.
A casting mold is then made of either a part of the dental arch that will receive the prosthesis, or the entire dental arch, using a supple material. A casting mold is also made of the portion of or entire dental arch that is directly antagonistic to the area that is to receive the implant. Based on these casting molds, a technician can then reproduce a dental model representing the gums, the teeth, and the stumps by casting the mold in a plaster-like material. Protruding pegs included in the casting penetrate into a base. These pegs can be removed and replaced into the base.
The technician then proceeds to cut from the mold the portion that is to receive the prosthesis, consisting of one stump in the case of a crown and two stumps separated by a cavity in the case of a bridge. The cavity is made by sawing the platform of the casting mold in a substantially transversal direction to the arch.
Traditionally, the technician removes from the casting mold the portion of the dental arch that is to receive the prosthesis and builds the prosthesis on this portion. As the prosthesis is being built, it can be repositioned on the casting mold to ensure that the two correspond. The prosthesis is placed onto the casting mold and adjusted with respect to the neighbouring teeth, adjacent teeth, and the arches in general.
In the case of a prosthesis that is built using three dimensional data of a dental model acquired by a mechanical or optical sensor, the prosthesis shape and size is calculated using the three dimensional data before being machined. However, a problem arises when a casting mold must be made of areas that are not easily accessible by a mechanical or optical sensor. For example, areas located between teeth are hard to access. Therefore, it may be hard to obtain the actual shape of the surface of certain teeth that are facing stumps, or the shape of certain areas of the stumps or adjacent teeth.